Diffusion burner



June 7, 1966 w. BRODLIN 3,254,695

DIFFUSION BURNER Filed Nov. 28, 1961 Willi Br'ddlin INVENTOR AGENT.

United States Patent DIFFUSION BURNER Willi Briidlin, Radolfzeller Str. 56, Allensbach (Bodensee), Germany 1 Filed Nov. 28, 1961, Ser. No. 155,373 Claims priority, application Germany, Nov. 29, 1960,

6 Claims. (Cl. 158-4) My present invention relates to a dilfusion-type burner for the combustion of liquid hydrocarbons such as fuel oils.

faces, formed for example by curved deflection plates, against which an injected fuel/air mixture is directed in order to promote the breakup of the liquid fuel into small droplets. In the past, however, such burners generally exhibited a tendency of burning with a noisy, soot-producing yellowish flame so that, in those instances where this type of combustion was not desired, burners utilizing more expensive fuels such as coal gas were given preference.

In my copending application Ser. No. 834,245, filed August 17, 1959, now abandoned, I have disclosed a burnor construction and a method of operation whereby a type of combustion similar to that of gas burners could be realized, the improvement residing essentially in the sep' aration of the larger droplets from the mixture prior to combustion and a further comminution of these droplets with reintroduction thereof into the injected stream.'

An object of my present invention is to provide an alternate solution to the problems stated above.

A more particular object of the invention is to provide a highly economical method of operating an oil burner in such manner that combustion can be maintained not only with a so-called silent, soot-free blue flame but also, if desired, with distinct infrared-radiation characteristics.

A further object of this invention is to provide an improved burner adapted to be operated in the manner indicated above.

I have discovered, in accordance with this invention,

It is known to provide oil burners with gasifying surthat the drawbacks of conventional constructions are large- 4 1y traceable to the fact that the fuel/air mixture initially admitted into the diifusion chamber contains an excess of air which escapes unutilized into the atmosphere and dis sipates a substantial part of the developing combustion heat Without useful effect.

A feature of the instant invention resides, therefore, in the operation of a diffusion-type oil burner in such manner that a fuel/ air mixture undersupplied with oxygen, preferably falling short by about 30% of the oxygen quantity stoichiometrically required for combustion, is admitted into a diffusion chamber and is heated therein by contact with a hot gasifying surface which may, if desired, also serve as a deflector to promote the dispersion of the liquid stream into minute particles.

The gasifying surface is advantageously maintained at a temperature of approximately 500 to 550 C. The gasified fuel/air mixture, whose fuel particles at this stage may have reached the consistency of an aerosol (i.e., may be capable of floating in stationary air), is then discharged in a multiplicity of fine jets through a perforated boundary wall of the diffusion chamber; this boundary wall is so positioned that a flame developed at its exterior, i.e., after the jets have been contacted with additional air to sup- 3,254,695 Patented June 7, 1966 plement the initial oxygen insufliciency, will heat the gasifying surface directly or by radiation in order to maintain it at the desired preheating temperature. The supply of the additional air may come simply from the atmosphere from which oil alone is discharged at a gauge pressure of,

say, 722 atm. while air is being supplied by a separate blower. Either system 'is adaptable for use with my invention so long as the air intake remains short of that required for complete combustion.

The heat necessary for maintaining the gasifying surface at its elevated temperature may be initially supplied by various means. Thus, an electric heating element may be temporarily energized at the start of operations, or combustion may be initiated first within the diffusion chamber itself with a supply of additional air which is later cut off. A partial combustion with resulting decomposition of the hydrocarbons may also be continuously maintained at the chamber entrance.

The invention will be further described With reference to the accompanying drawing in which:

FIG. 1 is an axial sectional view of an embodiment of the present invention taken substantially on the line I-I of FIG. 2;

FIG. 2 is a section taken on the line 11-11 of FIG. 1;

FIG. 3 is a detail view taken on the line III-III of FIG. 1;

FIG. 4 is a fragmentary view taken on the line IVIV of FIG. 2; and

FIG. 5 schematically illustrates an attachment for supplying an air/fuel mixture to the burner of the preceding 3b constitutes part of a diffusion chamber; the other (i.e.'

upper) extremity of duct 2b projects into the interior of a hood 1712 which encloses the remainder of the difiusion chamber of this burner and has an imperforate curved rear wall 17b. A starting heater 6b is disposed within the hood 17b adjacent the inserted upper end of duct 2b which acts as an atomizer and forms a cylindrical flowguiding surface. In order to increase the effective sur face area, duct 2b is provided in its inserted portion with a large number of radial bores 18b; these bores may, however, be omitted particularly in the case of larger installations. Duct2b is preferably made of a material of good thermoconductivity, e.g. a metal, and as shown is designed with relatively thick walls.

A perforated plate 4b of ceramic material forms a front or boundary wall of the hood 17b, parallel to the.

axis of duct 2b, and is provided with a multiplicity of passages 51) which are preferably very small pores with a diameter of 1 mm. or less. A fine-mesh radiation screen 15b, made from a nonoxidizing alloy, is positioned just outside the plate 412 with a slight spacing therefrom; this screen is supported by a series of flat bracing strips 16b, 16?) extending generally perpendicularly to it. Additional combustion air may, if desired, be admitted into the region beyond plate 412 by means here illustrated as a conduit 32b.

The connection between nozzle 11) and the outer end of duct 2b is formed by an apertured cap 21b having erforations 221). These perforations, whose effective overall area may be adjustable by means not further illustrated, serve for the admission of additional air into the region just ahead of the duct 212, it being understood that the total air quantity from channel 261) and perforations 22b will be short of that required for complete combustion of the fuel injected via channel 1%, as previously explained. The air and fuel streams injected by the nozzle may be under a pressure of about 0.1-0.5 atm. gauge (preferably not more than 0.2 atm. gauge). The wall thickness of cap 21b is very limited for the purpose of thermally insulating the hot duct 2b from the nozzle 1b.

In operation, the duct 2b should be maintained at a temperature of at least 200 C., preferably 500550 C. The flame developed in front of plate 412 at the grid 15b will generally radiate enough heat toward the inserted upper end of the duct to maintain it at the desired temperature level, a heat reflector 4% being provided at the top of hood 17b to assist in the action by directing heat rays from the region of plate 4b toward the nozzle 15, as shown in FIG. 1; additionally, however, a partial combustion may be maintained within cap 21b which will give rise to an annular flame forming a vortex around the nozzle mouth as indicated by the arrows 3311. This flame, whose extent is limited by the undersupply of oxygen, causes a decomposition and partial oxidation of the injected fuel into carbon monoxide and hydrogen which, upon their subsequent combustion at the grid 15b, gives rise to a particularly quiet flame without soot. The burner shown in FIGS. 1-4 can, therefore, be operated without a flue for the escape of combustion gases. The partial combustion within cap 2112 can be brought about by suitable ignition means such as a pair of electrodes 14b.

FIG. shows an attachment for supplying fuel and air to a nozzle, here designated 101, which is representative of the nozzle shown in the preceding figures. An oil reservoir 124 is connected by conduits 119 and 120 to the corresponding channels of nozzle 101. Air under pressure is delivered to reservoir 124 by a blower 123. Part of this air is passing out of the reservoir through conduit 129 while the remainder creates suflicient pressure to drive oil at the desired rate through the channel 119. The oil may, of course, be supplied continuously or intermittently from a suitable source not shown. The pressure of blower 123 may be of the order of 0.1-0.3 atm. gauge.

My invention is not limited to the specific embodiment described and illustrated but may be realized in various modifications except as otherwise limited by the appended claims.

I claim:

1. A burner comprising a diffusion chamber provided with a boundary wall having a multiplicity of perforations, atomizer means forming a generally cylindrical flow-guiding surface in said chamber with an axis substantially parallel to said wall and positioned to be heated by radiant energy emitted by said wall upon the existence of a flame at the exterior of said wall, a significant part of said surface being separated from said boundary wall by a substantially empty space enabling the direct passage of radiant heat from said wall to said surface, said atomizer means including an elongated upright duct with an open-topped upper portion projecting from below into said chamber, said duct bein imperforate below said chamber and provided with a multiplicity of radial bores throughout said upper portion thereof, injector means for admitting into said chamber through said duct a flow of combustible liquid hydrocarbons directed into contact with said surface, intake means adjacent said injector means for admixing with said flow a supply of air having an oxygen content which falls short of the stoichiometric quantity required for the combustion of said hydrocarbons, means including said boundary wall preventing the admission of additional oxygen into said chamber, and means including said boundary wall for preheating said flow in its passage along said surface to maintain said flame by facilitating the ignition of streams of combustible air/hydrocarbon mixture emerging from said wall through said perforations.

2. A burner according to claim 1 wherein said chamber comprises a hood, said duct being provided with an extremity opening into said hood, said injector and intake means being positioned at a location of said duct remote from said extremity, said boundary wall forming part of said hood.

3. A burner comprising a diffusion chamber provided with a boundary wall having a multiplicity of perforations, atomizer means forming a generally cylindrical flow-guiding surface in said chamber with an axis substantially parallel to said wall and positioned to be heated by radiant energy emitted by said wall upon the existence of a flame at the exterior of said wall, a significant part of said upper portion being separated from said boundary wall by a substantially empty space enabling the direct passage of radiant heat from said wall to said surface, injector means for admitting into said chamber through said duct a flow of combustible liquid hydrocarbons directed into contact with said surface, intake means adjacent said injector means for admixing with said flow a supply of air having an oxygen content which falls short of the stoichiometric quantity required for the combustion of said bydrocarbons, means including said boundary wall preventing the admission of additional oxygen into said chamber, and means including said boundary wall for preheating said flow in its passage along said surface to maintain said flame by facilitating the ignition of streams of combustible air/hydrocarbon mixture emerging from said wall through said perforations, said chamber comprising a hood, said atomizer means comprising an elongated duct provided with an extremity opening into said hood, said injector and intake means being positioned at a location of said duct remote from said extremity, said boundary wall forming part of said hood, said hood being further provided with fine-mesh screen closely spaced from said boundary wall and positioned externally thereof.

4. A burner comprising a hood-shaped diffusion chamber provided with a curved solid rear wall and a perforated front wall, an elongated upright duct with an open-topped upper portion projecting from below into said chamber, a significant part of said upper portion being separated from said front wall by a substantially empty space enabling the passage of radiant heat from said front wall to said'duct through said chamber, injector means for admitting into the lower end of said duct below said chamber a flow of combustible liquid hydrocarbons directed upwardly into said chamber, intake means adjacent said injector means for admixing with said flow a supply of air having an oxygen content which falls short of the stoichiometric quantity required for the combustion of said hydrocarbons, and means including said first wall for preheating the flow of air/hydrocarbon mixture in said duct.

5. A burner according to claim 4, further comprising heat-reflection means for directing heat from the region of said front wall toward said injector means.

6. A burner according to claim 4 wherein said duct is imperforate below said chamber and is provided with References Cited by the Examiner UNITED STATES PATENTS Buchholtz 158-4 Edmonds 15 856 Moors 158-53 Parker et a1 158117.5 Parker et a1. 1585 Cannon 1584 X Johnson 158--8 X 6 r Farrell 158-53 Sherman 1584 Lambert 15899 X Mentel et al 158114 Klein 158-114 X France.

10 FREDERICK L. MATTESON, JR., Primary Examiner.

JAMES W. WESTHAVER, Examiner. 

1. A BURNER COMPRISING A DIFFUSION CHAMBER PROVIDED WITH A BOUNDARY WALL HAVING A MULTIPLICITY OF PERFORATIONS, ATOMIZER MEANS FORMING A GENERALLY CYLINDRICAL FLOW-GUIDING SURFACE IN ASAID CHAMBER WITH AN AXIS SUBSTANTIALLY PARALLEL TO SAID WALL AND POSITIONED TO BE HEATED BY RADIANT ENERGY EMITTED BY SAID WALL UPON THE EXISTENCE OF A FLAME AT THE EXTERIOR OF SAID WALL, A SIGNIFICANT PART OF SAID SURFACE BEING SEPARATED FROM SAID BOUNDARY WALL BY A SUBSTANTIALLY EMPTY SPACE ENABLING THE DIRECT PASSAGE OF RADIANT HEAT FROM SAID WALL TO SAID SURFACE, SAID ATOMIZER MEANS INCLUDING AN ELONGATED UPRIGHT DUCT WITH AN OPEN-TOPPED UPPER PORTION PROJECTING FROM BELOW INTO SAID CHAMBER, SAID DUCT BEING IMPERFORATE BELOW SAID CHAMBER AND PROVIDED WITH A MULTIPLICITY OF RADIAL BORES THROUGH SAID UPPER PORTION THEREOF, INJECTOR MEANS FOR ADMITTING INTO SAID CHAMBER THROUGH SAID DUCT A FLOW OF COMBUSTIBLE LIQUID HYDROCARBONS DIRECTED INTO CONTACT WITH SAID SURFACE, INTAKE MEANS ADJACENT SAID INJECTOR MEANS FOR ADMIXING WITH SAID FLOW A SUPPLY OF AIR HAVING AN OXYGEN CONTENT WHICH FALLS SHORT OF THE STOICHIOMETRIC QUANTITY REQUIRED FOR THE COMBUSTION OF SAID HYDROCARBONS, MEANS INCLUDING SAID BOUNDARY WALL PREVENTING THE ADMISSION OF ADDITIONAL OXYGEN INTO SAID CHAMBER, AND MEANS INCLUDING SAID BOUNDARY WALL FOR PREHEATING SAID FLOW IN ITS PASSAGE ALONG SAID SURFACE TO MAINTAIN SAID FLAME BY FACILITATING THE IGNITION OF STREAMS TO MAINTAIN SAID AIR/HYDROCARBON MIXTURE EMERGING FROM SAID WALL THROUGH SAID PERFORATIONS. 